Test Equipment Anonymous

What is it? An ATU - Antenna Tuning Unit.

Stay away from model railways. It's a slippery slope. You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

Zenith wrote: ↑Thu Feb 05, 2026 1:50 pm You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

EC8010 wrote: ↑Thu Feb 05, 2026 1:49 pm Looks like a very nicely made capacitance decade box. Tinsley or Muirhead? But the decade switches would ideally have been built on a lower loss material than I see in the photograph. Clear Perspex would be a good replacement. But it would take considerable time to do the job.

It is elegant, isn't it. It is a Sullivan C8700, up to 1.11µF, 3 decade plus a rotary decade, wax covered mica 0.1%.

Quick measurements on an old Marconi TF2700 (1%) show it is working and a low dissipation factor. One knob has been broken and crudely epoxied together, but still slipped on the shaft. I've cured the slipping by crudely epoxying a pop-rivet stem into the holes.

There is no way I would do more: too little benefit, too many other things to do.

Ah, forgot Sullivan. Just as good, if not better. Years ago, I (stupidly) failed to rescue a beautiful Sullivan 1nF variable capacitor. Alright, it was a bit big (about a 10" mahogany cube), but still. It had a Vernier scale and slow motion drive.

I think I've fixed the XP machine's erratic booting. It had a SATA CD drive. Not any more. It now has CD drive on parallel bus (which works just fine).

EC8010 wrote: ↑Thu Feb 05, 2026 1:54 pm

Zenith wrote: ↑Thu Feb 05, 2026 1:50 pm You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Not so much these days. I came across someone building a 5½" gauge locomotive in his garage. A lot of the difficult parts such as cylinders and the complicated linkages were made to his specification by an engineering works with CNC tooling. You can argue that isn't really scratch building, but even way back scratch builders would have bought in a few things, such as gears, motors and so on.

That's cheating. The whole point of making a steam engine is to learn how to do the various manufacturing processes and improve your skills. I'll agree that hobbing gears is best farmed out, but the rest is all perfectly doable.

I've just scrapped the (presumed duff) SATA CD drive and it yeilded a pair of precision ground/honed 2.99mm silver steel rods that the laser sled ran on. I don't have tools for honing (too big) or precision grinding (too messy), but I can make nice low friction sleeves to use those two shafts as bearings.

Zenith wrote: ↑Thu Feb 05, 2026 1:50 pm What is it? An ATU - Antenna Tuning Unit.

Stay away from model railways. It's a slippery slope. You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

I had a 16ft*8ft box room as a kid, 8ft high on one side, 2ft high on the other. That was, of course Not A Problem for Me. It was filled with model railway and scalextrix, at different times. I marvelled at people who scratchbuilt stock and sets. I saw one article about the Pendon museum; later, much later, I finally managed to go there https://pendonmuseum.com/ Took daughter once, and seeing someone make cauliflower inspired her to do some modelling, which I still have. Good times.

I still have the track and stock, but have no desire to resurrect it. Whenever I get urges in that direction, I play this: https://www.openttd.org/about The original 1993 game was groundbreaking, and kept me amused while commuting to Palo Alto It was so playable that people eventually cloned it and significantly enhanced it.

EC8010 wrote: ↑Thu Feb 05, 2026 1:54 pm

Zenith wrote: ↑Thu Feb 05, 2026 1:50 pm You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Or a local hackspace. Much cheaper, and with a supply of knowledgeable people on tap.

Zenith wrote: ↑Thu Feb 05, 2026 2:35 pm

EC8010 wrote: ↑Thu Feb 05, 2026 1:54 pm

Zenith wrote: ↑Thu Feb 05, 2026 1:50 pm You'll end up scratch building locomotives and rolling stock from the original blueprints. I've seen it happen.

And that means you need a machine shop. Very useful, but expensive.

Not so much these days. I came across someone building a 5½" gauge locomotive in his garage. A lot of the difficult parts such as cylinders and the complicated linkages were made to his specification by an engineering works with CNC tooling. You can argue that isn't really scratch building, but even way back scratch builders would have bought in a few things, such as gears, motors and so on.

My father used to have a bound set of (1920s?) magazines describing how to build a car from scratch. Naturally that included instructions on how to build the necessary tooling from scratch.

Ah yes, tooling. I frequently make tools in the workshop to enable further workshop tools to be made to make test equipment for the lab to develop something that will play music. Maybe. As an example, I made a D-bit to drill a tapered hole for the box that stores collets for my (home-made) tapping fixture that ensures that I tap holes true. The tapping fixture was used this week to tap M2.5 holes for a voltage reference that will become part of a low noise bench supply. In turn, the low noise supply will enable noise measurements, eventually leading to some low noise audio electronics. I find making accurate swarf very therapeutic.

Life was a lot tougher for 1920s modellers. Their lathe was highly unlikely to be electrically powered. Probably treadle. On the other hand, the materials they machined were pretty soft (which is why classic cars and motorcycles wear so quickly). But if you really want to see feats of improvisation, look at 1940s papers by the scientists experimenting with ionising radiation; they had to make everything.

EC8010 wrote: ↑Thu Feb 05, 2026 5:38 pm Life was a lot tougher for 1920s modellers. Their lathe was highly unlikely to be electrically powered. Probably treadle.

Not just modellers.

There's a decent "museum of Icelandic life" in Vik. I remember talking to the person who set it up, after spending a lifetime wandering around Iceland collecting things that were likely to be forgotten.

One of the things on display was a 1930s pelton wheel. The farmer had decided to find out what this newfangled electricity could do, so he built his hydroelectricity plant from scratch, including the pelton wheel.

If you don't visit Iceland and come back a slightly different person for several different reasons, then you haven't been paying attention.